U.S. patent number 4,253,971 [Application Number 06/081,091] was granted by the patent office on 1981-03-03 for water treatment.
Invention is credited to Norman A. MacLeod, Charles P. N. Webb.
United States Patent |
4,253,971 |
MacLeod , et al. |
March 3, 1981 |
Water treatment
Abstract
A method of controlling pathogenic organisms, fungi and algae in
water which includes the steps of applying to the water a primary
reagent comprising a linear polymeric biguanide or a salt thereof
which in its free base form has a recurring polymer unit
represented by the formula ##STR1## wherein X and Y represent
bridging groups in which together the total number of carbon atoms
directly interposed between the pairs of nitrogen atoms linked by X
and Y is more than 9 and less than 17, and a back-up algicidal
agent comprising a substance which in the aqueous phase produces
hydrogen peroxide, preferably persalts selected from perborates,
percarbonates, peroxides and persulphates.
Inventors: |
MacLeod; Norman A. (Northcliff,
Transvaal, ZA), Webb; Charles P. N. (Illovo,
Johannesburg, Transvaal, ZA) |
Family
ID: |
25571690 |
Appl.
No.: |
06/081,091 |
Filed: |
October 2, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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916048 |
Jun 14, 1978 |
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Foreign Application Priority Data
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Jun 14, 1977 [ZA] |
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77/3557 |
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Current U.S.
Class: |
504/122; 424/613;
424/616; 424/715; 210/759; 210/764; 424/615; 424/660; 504/123 |
Current CPC
Class: |
C02F
1/722 (20130101); C02F 1/50 (20130101); C02F
2103/42 (20130101) |
Current International
Class: |
C02F
1/50 (20060101); C02F 1/72 (20060101); C02F
001/72 (); C02F 001/50 () |
Field of
Search: |
;210/60,63R,64,169,501
;71/67 ;424/130 ;162/161 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2735393 |
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Feb 1978 |
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DE |
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50-105906 |
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Jun 1975 |
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JP |
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1407258 |
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Sep 1975 |
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GB |
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1500707 |
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Feb 1978 |
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GB |
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Primary Examiner: Therkorn; Ernest G.
Attorney, Agent or Firm: Haseltine and Lake
Parent Case Text
This is a continuation of application Ser. No. 916,048 filed June
14, 1978, now abandoned.
Claims
We claim:
1. A method of controlling pathogenic organisms, fungi and algae in
water which comprises the steps of applying to the water a primary
reagent comprising a linear polymeric biguanide or a salt thereof
which in its free base form has a recurring polymer unit
represented by the formula ##STR4## wherein X and Y represent
bridging groups in which together the total number of carbon atoms
directly interposed between the pairs of nitrogen atoms linked by X
and Y is more than 9 and less than 17, followed by applying to the
water an alkali metal perborate in tablet form to produce a back-up
algicidal effect in the water, and which in the aqueous phase
produces hydrogen peroxide.
2. A method according to claim 1 in which the primary reagent is
poly(hexamethylene biguanide) hydrochloride.
3. A method according to claim 1 in which the primary reagent is
applied to the water at a dosage of between 4 to 12 ppm.
4. A method according to claim 3 in which the dosage of the primary
reagent is about 10 to 12 ppm.
5. A method according to claim 1 in which the perborate is sodium
perborate.
6. A method according to claim 1 in which the tablets are slow
release tablets.
7. A method according to claim 1 in which the perborate is applied
to the water in such manner as to produce a concentration of
hydrogen peroxide in the water of between 0.5 and 10 ppm.
8. A method according to claim 1 in which the perborate is an
alkali metal perborate and is applied to the water at a dosage of
between 100 to 600 grams of the hydrogen peroxide producing
substance per 50,000 liters of water per week.
9. A method according to claim 8 in which the dosage is
substantially 200 grams of the alkali metal perborate per 50,000
liters of water per week.
Description
BACKGROUND OF THE INVENTION
This invention relates to water treatment and particularly to the
treatment of swimming pool water.
Swimming pool water is usually maintained clean and free of
bacteria, fungi and algae by means of chlorination. A typical
chlorination reagent is calcium hypochlorite. However the bacteria,
fungi and algae become resistant to a consistent level of
chlorination over a period of time and it is therefore necessary to
treat the water periodically with an agent which is capable of
dealing with the resistant bacteria, fungi and algae. Such an agent
is known as a super-chlorination or back-up agent.
In the specification of South African Pat. No. 73/9529, the
contents of which are incorporated herein by reference, there is
described a method of treating water for controlling the growth of
bacteria and algae in which a suitable quantity of a linear
polymeric biguanide or a salt thereof which in its free base form
has a recurring polymer unit represented by the formula ##STR2##
wherein X and Y represent bridging groups in which together the
total number of carbon atoms directly interposed between the pairs
of nitrogen atoms linked by X and Y is more than 9 and less than
17. A preferred polymeric biguanide is poly(hexamethylene
biguanide) hydrochloride sold under the trade name Baquacil SB by
Imperial Chemicals Industries Limited. This water treatment method
has the advantage that it is completely chlorine free and has no
irritant effect on the eyes. In addition no objectionable odors or
tastes are produced.
In certain circumstances however which may vary greatly according
to local conditions back-up treatment may be required to assist the
algicidal activity of the polymeric biguanide. The problem exists
however with this reagent that most of the currently available
back-up agents are not compatible with this reagent and as a result
chemical degradation occurs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
method of treating water.
According to the invention a method of controlling pathogenic
organisms, fungi and algae in water includes the steps of applying
to the water a primary reagent comprising a linear polymeric
biguanide or a salt thereof which in its free base form has a
recurring polymer unit represented by the formula ##STR3## wherein
X and Y represent bridging groups in which together the total
number of carbon atoms directly interposed between the pairs of
nitrogen atoms linked by X and Y is more than 9 and less than 17,
and a back-up algicidal agent comprising a substance which in the
aqueous phase produces hydrogen peroxide.
The combined treatment results in effective control of pathogenic
organism, fungi and algae in the water.
DESCRIPTION OF PREFERRED EMBODIMENTS
The primary reagent may be any linear polymeric biguanide or salt
thereof described in the specification S.A. Pat. No. 73/9529 and is
preferably poly(hexamethylene biguanide) hydrochloride.
As described in the specification of South African Pat. No. 73/9529
the concentration of the polymeric biguanide or salt thereof in the
water should preferably not be below 4 ppm, and a concentration of
about 10 to 12 ppm is found to be effective, but the period for
which an effective concentration is maintained depends inter alia
on the climatic conditions and the number of persons using the
swimming pool.
The hydrogen peroxide producing substance may be a persalt of the
following type:
1. A higher oxide
2. A peroxygen compound
3. An addition compound of the form X.Y.H.sub.2 O.sub.2
4. A true peroxy compound.
These compounds have similar properties but they are not easily
classified in strict chemical terms.
1. Higher Oxides
The term "high" has little precision but is usually applied in
those cases where an element forms well marked basic acidic or
amphoteric oxides (normal oxides) and also oxides with a greater
proportion of oxygen than the normal oxides. A typical example of a
higher oxide is sodium peroxide.
2. Peroxygen Compounds
Potassium monopersulphate (peroxy monosulphate) is a true peroxygen
compound. The standard electro potential (E.degree.) is 1.44 volts.
The persulphate dissociates in water to produce two electrons:
3. Addition Compounds
Sodium percarbonate is not a true persalt but an addition compound,
i.e. it may be considered as 2NA.sub.2 CO.sub.3 . 3H.sub.2 O.sub.2.
In solution dissociation occurs into sodium carbonate and hydrogen
peroxide.
4. True Peroxy Compounds
Sodium perborate is a white crystalline powder manufactured in two
forms. The most widely used is known as the tetrahydrate
NaBO.sub.3. 4H.sub.2 O, which is often described as NaBO.sub.2.
H.sub.2 O.sub.2. 3H.sub.2 O.
The second form is known as the mono-hydrate NaBO.sub.3. H.sub.2 O
and may be written NaBO.sub.2. H.sub.2 O.sub.2. According to T. D.
Manley (J.C.I. Jan. 6, 1962 14) the nmr spectra and electrolytic
evidence points to the structure of the hydrates as being true
peroxy rather than the crystalline compounds which would have been
peroxyhydrates. The anhydrous perborate is different, since it
evokes its oxygen in water and is probably a disubstituted
peroxide.
Preferred persalts are perborates, peroxides, percarbonates and
persulphates. The persalts may be in the form of any suitable salt,
but are typically alkali metal or alkaline earth metal salts.
Usually the salts will be sodium or potassium salts.
The preferred substance for the back-up agent is an alkali metal
perborate, e.g. sodium or potassium perborate. The alkali metal
perborates, particularly sodium perborate, have the advantages that
they are generally freely available, inexpensive and that they have
a low mammalian toxicity and a satisfactory cost/efficacy
ratio.
The back-up agent may be applied to the water as a powder or in
tablet form. The tablet form is preferred for the tablets are easy
to handle and can be supplied as slow release tablets.
The back-up agent is generally applied to the water in such manner
as to produce a concentration of hydrogen peroxide in the water of
between 0.5 and 10 ppm. The amount of hydrogen peroxide producing
substance necessary to produce this concentration will depend on
the nature of the substance. By way of example it can be stated
that where the hydrogen peroxide producing substance is an alkali
metal perborate, the perborate is usually applied to the water at a
dosage of between 100 to 600, preferably 200, grams per 50,000
liters of water per week.
The invention is further described in the following examples.
Two pools A and B with water volumes of 70,000 liters and 150,000
liters respectively were treated over a three month period
extending from November of one year to March of the following
year.
The pools were treated with a primary reagent of poly(hexamethylene
biguanide) hydrochloride in the form of a 20% aqueous solution to
provide a concentration of 50 ppm of the solution, that is a
concentration of 10 ppm of the active ingredient, and with slow
release sodium perborate tablets each having an average mass of 225
grams, on a four month cycle, as follows:
______________________________________ FOUR MONTH CYCLE Amount of
Amount of Biguanide Reagent Biguanide Reagent Tablets Tablets Pool
(liters) Tablets (liters) Tablets
______________________________________ First Month Second Month
______________________________________ A 4.75 5 2.5 6 B 15.0 12 8.0
6 ______________________________________ Third Month Fourth Month
______________________________________ A 2.55 3 0.5 7 B 6.7 9 3.5
12 ______________________________________
The analytical and microbiological observations are recorded in the
accompanying table.
TABLE
__________________________________________________________________________
SAMPLING DATES POOL 22/11 29/11 6/12 13/12 16/1 7/2 21/2 7/3
__________________________________________________________________________
CHEMICAL PROPERTY Hardness Temporary as CaCO.sub.3 ppm A 148 190
190 186 167 160 166 140 B 71 75 83 75 78 35 32 78 Hardness
Permanent as CaCO.sub.3 ppm A 64 68 66 62 62 40 42 36 B 43 46 44 39
42 35 32 35 Ammonia as N ppm A -0.01 -0.01 0.37 0.65 1.54 0.9 0.57
0.74 B 0.01 0.01 0.24 0.75 0.25 0.24 0.74 0.29 Nitrite as NO.sub.2
ppm A -0.05 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 B -0.05 -0.1 -0.1
-0.1 -0.1 -0.1 -0.1 -0.1 Nitrite as NO.sub.3 ppm A 8.9 8.4 10.0
11.0 9.0 3.5 4.8 6.7 B 0.2 0.8 0.5 0.3 0.1 0.1 0.1 0.2 Albuminoid
Nitrogen ppm A 0.36 0.49 0.82 1.15 1.44 1.23 1.15 1.85 B -0.01
-0.01 0.49 0.65 0.82 0.90 1.07 1.30 Boric Acid as Boron A -0.01 0.5
0.65 0.75 1.6 1.9 3.0 2.7 B 0.3 0.7 0.75 1.0 1.1 1.9 3.7 2.7
MICROBIOLOGICAL RESULTS Total Count (1 ml at A 3 3 1 1 22 6 6 20
37.degree. C. 24 hours) B TNTC 54 14 17 15 0 0 4 Total Coliform
(per 100 ml) A 0 0 0 0 0 0 0 0 B 2 0 0 0 0 0 0 0
__________________________________________________________________________
The tabulated results indicate that the use of the primary reagent
of poly(hexamethylene biguanide) hydrochloride together with a
back-up agent of sodium perborate satisfactorily controlled
pathogenic organisms.
Observations to detect algal growth were made throughout the test
period. The test period extended through the summer months with
average temperatures varying from 21.degree. C. to 28.degree. C.
The test pools were used extensively during the test period. Visual
examination of the pools showed no evidence of algae or fungi. The
chemical properties tabulated in the table indicate that the pool
treatment of the invention produced no deleterious side
effects.
The tablets used in the example were prepared by compressing sodium
perborate powder at a pressure of approximately 5,000 kilograms per
square centimeter. The rate at which the tablet dissolves in water
is proportional to the compressive force used in the forming of the
tablet. Alternatively the sodium perborate powder can be made into
a tablet using a polyethylene glycol wax as a lubricant.
The sodium perborate tablet is safe to handle and is non-toxic and
generates no smell or obnoxious fumes. It is simple to use,
obviates the need for algicides which generate ammonia, and creates
no harmful breakdown products in the pool. The tablet dissolves
slowly and so is more effective in cleansing and in disinfecting
than if the sodium perborate were released in a sudden burst.
Since the hydrogen peroxide is only released when the tablets are
dissolved there are significant reductions in the hazards of
handling and storage compared to the position that would result if
liquid hydrogen peroxide (at commercial concentrations) were used
as a back-up agent.
By experiment it has been found that the sodium perborate works
particularly effectively as a back-up agent when applied to the
water at a dosage of approximately 200 grams per 50,000 liters of
water per week.
However in winter when the rate of algal growth diminishes a sodium
perborate dosage of as low as 100 grams per 50,000 liters per week
can produce satisfactory results. Conversely when a pool which is
severely affected by algal growth is first treated with the method
of the invention, initial shock doses of up to three times the
normal dosage of sodium perborate may be required to control the
situation. Thus a dosage of up to 600 grams per 50,000 liters per
week may be required.
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